February 2011 Chevy High Performance Q&A

Luck, Where Preparation Meets Opportunity

For some, luck is just something that happens to them; others have to make their own. Just ask Warren Johnson, the “Professor” in the NHRA Pro Stock ranks. He has been preaching the above headline for as long as I can remember. This month I have two stories; one is racing related, and the other is about hauling our possessions down the road.

2/2

First, my good friend Greg Ventura and his dad, Al, were at an NHRA National event, running their Super Gas Nova. Greg called me after his third time hit going into eliminations. The car had performed flawlessly over the three runs, but while he was in the trailer recording his run and weather conditions, his dad stuck his head in and said, “We’ve got fluid running out from under the car!” The Powerglide transmission case had completely cracked around the low gear band adjustment screw, and the fluid was pouring out. Luckily, it made the run and didn’t leave fluid on the track.

As luck would have it, they came prepared with a spare Powerglide transmission. After swapping out the trans and driving around the pits, everything was ready to go. There was only one little problem: The original transmission used a 1.96 First gear to help get the small-block–powered Nova moving out the beams and accelerating in First gear. The backup was a racing-built trans but it only had a stock 1.76 First gearset. Greg was wondering what this would do to his performance, since he had never run this transmission ratio in the car. We talked our way through the changes and came up with a strategy for his starting line delay and a throttle stop setting to adjust for the higher gear ratio. This is where the preparation comes back into the story. For all the adjustments that Greg and I came up with, we missed it by about 50 percent. His reaction time was slower than we expected, and the on-track performance was about .02 slow. He lost the first round, but it taught us a valuable lesson. Next time, he’ll know what number to put into the car to work with the higher gear ratio. It wasn’t enough to be prepared with a spare trans; he also needed the data. It costs us way too much money to race these cars without giving ourselves a chance to win.

Obviously, preparation not only applies to your racing endeavors, but also in getting us to and from the track. While Greg was off running the National, Daniel, Lisa, and I had struck off to run the Pacific Street Car Association race in Las Vegas (we had a decent weekend, with us both going rounds). On our way home Sunday, we had a blowout on one of the tires on our 24-foot Pace trailer. The trailer has more than 50,000 miles on it, and it’s on its second set of tires. (Note that I always check the tire pressure on all of our rubber before long trips.) As Daniel and I were swapping out the trailer tire, we found that the small floor jack I was carrying would not pick up the 8,000-pound trailer to get the tire off. I was able to steal the scissor jack out of my 3/4-ton Chevy truck to assist. I had only had one other issue with a tire in the 13 years on this trailer, and I’d had a bottle jack with me at the time. Being prepared for anything while you’re on the road is very important.

Check your rigs for everything you would need to get you and your families back on the road. The last thing you want is to be stranded with all your worldly possessions. Also, make sure you have some way to lock up your trailer tongue to prevent someone driving away with it. You never know, you may end up having to run into the next town with your truck and leave your trailer on the side of the road. That would be one bad feeling driving up to where you left your trailer to find it gone! Always be prepared.

Icing

I’ve read a few articles that make mention of icing problems when using an Edelbrock Air-Gap intake. I have no idea what that means. The person I bought my intake from said he cooked his engine because of icing. I asked if he was putting a bag of ice on the intake between runs and the answer was no, not that type of icing. Would you please explain? Thanks.

Michael CoppBrighton, MI

Carburetor icing is just about a thing of the past. Back in the day, when our cars were all carbureted, it was a regular condition in very cold climates. Moisture in the air passing through the carburetor would freeze and the ice adhered to the throttle blades, due to the lack of heat in the intake air and to the manifold because of the elimination of the exhaust crossover in the Air-Gap-style manifolds. This crossover is removed to boost performance by lowering the inlet charge temperature. In the winter months, the cold air comes through the carburetor, and the velocity increases in the venturi boosters, drawing the atomized fuel into the airstream, which lowers the temperature of the air to the freezing point. The throttle blades are in the way of the airflow and the moisture is deposited on the blades in the form of ice. This can be very dangerous, causing the throttle blades to be held open and not return to idle. The ice can also plug idle transfer slots in the carburetor body, causing the engine vacuum to draw directly on the idle circuit of the car which causes the engine to run quite rich.

We’re not sure how the previous owner of your manifold blew his engine because of carburetor icing. We’ve only seen the engines go rich when this happens. When you go to wide-open throttle, the ice causes a small restriction to airflow and the fuel and air get to the engine. The only true remedy to carburetor icing is to introduce heat into the airstream of the engine. Our high-flow, open-element air cleaners that give us great performance feed the engine cold air. You could run some type of air cleaner housing in the winter to add exhaust system heat to the intake air. You can also try to add a lubricant to the fuel, which will coat the throttle blades with slippery stuff, preventing the ice buildup. A good top end lubricant, such as Marvel Mystery Oil, added to your fuel during the winter months can help, but will not prevent icing in very cold high-humidity conditions. It is much easier than rigging up some type of heated induction system. Good luck!

Which Intake/Carb for a 283?

I’m doing my first complete engine rebuild for a friend’s ’62 Impala two-door with a 283 that was purchased recently. He wanted to keep the 283 for the authenticity. This car will probably never hit the track, so a larger-displacement engine is not needed. However, that doesn’t mean we don’t want this 283 to be decent when stepping on the go-pedal. The block was stripped and sent to the machinist. After being inspected, the machinist informed us we could go 0.040-inch over on the pistons. My friend bought regular cast flat-top pistons and gave them to the machinist for boring/honing, along with decking. The original valvetrain and heads (3814480) will be reused. The crank (3735236) has been turned 10/10, and the rods checked well. The hydraulic camshaft we’re planning on using has a cam lift of 0.281 intake and 0.296 exhaust, lobe centerline of 107 intake and 117 exhaust. Duration at 0.050-inch tappet lift is 204 intake and 214 exhaust. The engine had a set of headers, but since there aren’t a lot of header options available for a ’62, I think these are Hookers. The previous owner(s) removed the Powerglide and installed a TH350 auto. That’s the background info, and now for the questions.

We purchased standard 0.040-inch-over rings, but I will be double-checking the endgaps. What’s a good endgap to look for with the first, second, and oil rings? We’re planning on keeping it a true dual exhaust; what size piping would be good so not to lose bottom-end torque? Since getting the block and pistons back, I tried checking the piston-to-wall clearance. With most pistons not being perfectly round, I was getting a different feeler gauge reading depending on where I was checking. What’s a good clearance, and where do you check it: on the skirt or wristpin side; top of the piston by the lands, below the lands, or bottom of the piston?

Finally, based on our rebuild, what intake and carb would you recommend to take this 283 to its full potential? The only caveat is an electric choke, and we’re not opposed to Summit brand parts. Thank you for your contribution to Chevy High Performance.

Michael LynchVia email

The 283 is a great place to start your engine-building career. They are quite simple and there is plenty of information out there to support your build. You can either reference How to Rebuild Your Small-Block or get information from all over the Internet and you will be in good shape. Let’s take your questions in the order you served them up.

It’s always a good idea to check the piston ring endgap on assembly. Usually the only time you need to grind the ring endgap for the proper fit is when you buy oversized rings. A 0.040-inch overbore isn’t that common for file-fit piston rings. If you were to have file-fit rings for your engine, they would be 0.045-inch oversize. For a standard street rebuild, we would use the standard rule of thumb of 0.004-inch endgap per inch of bore. With your 3.790-inch overbore, that puts your top ring right at 0.015-inch endgap. For the second ring you’ll want slightly more clearance than the top. We’d recommend going with 0.018 inch for the second. This is to prevent the top ring from being lifted off the top ring land if the top ring leaks some compression gases and pressurizes the area between the top and second ring. Finally, the oil ring segments have a very wide tolerance. The chrome segments can range from 0.015 to 0.050 inch. Yes, it’s better to be on the smaller side, but it’s not imperative.

With your build, your Mouse is going to produce around 240-250 hp. This engine will work very well with a 2-inch dual exhaust. If you wish, you can go as large as a 21/4-inch tube. It would be nice if you could add a balance pipe between the two banks of the exhaust system. The Impalas are built on what is called an X-frame, which prevents you from getting from side to side under the vehicle. You’re spot-on that the bigger you get the more slow speed torque you’re going to give away. The last time we checked, the ’62 Imps aren’t very light!

As you have found out, checking piston-to-wall clearance with a feeler gauge can be tricky. Piston manufacturers give you a gauge point to set the cylinder wall clearance. This is where you would measure the piston with an outside micrometer. Early forged pistons used a gauge point perpendicular to the wristpin. Most current forged pistons use a gauge point at 1/2 inch up from the end of the piston skirt. You see differing locations to measure the piston because of the cam-ground piston skirt. (This grinding allows the piston to grow as it heats up and become round to match the cylinder bore.) This is why you always want to get the engine up to operating temperature before putting high load on the engine. The cam ground skirts give your engine quieter operation during cold starts. Finally, cast pistons like those you are using also have specific cam-ground skirts, but cast pistons don’t grow as much as forged alloy pistons, so you can run much tighter piston-to-wall clearances with cast pistons. The pistons you used should have had a sheet with them to spec out the specific clearance and where to measure the clearance. If you have between 0.002 and 0.003 inch of clearance with a feeler gauge you should be fine. This is as you slide the piston down the cylinder with the gauge between the bottom of the skirt, 90 degrees from the wristpin axis. You will check this clearance from the bottom of the piston, centered in the skirt. Slide the feeler gauge into the cylinder, then try to slide the piston into the bore. Start on the small side (0.0015 inch) and increase the gauge size until a good tension is on the piston to slide it into the bore.

Let’s get down to your final question. We’d use an Edelbrock Performer intake manifold PN 2101. This has two different-sized intake runners between the upper and lower planes, to help broaden the torque curve and gain area under the curve. This will help move your Imp. For a nice carburetor, go with an Edelbrock Thunder Series AVS 500-cfm carburetor PN 1801; it features Air Valve secondaries that deliver proper airflow to the engine based on demand. As the engine speed increases, the secondary air valve opens to increase the airflow potential. The benefit of this type of carburetor is that the engine is never over-carbureted throughout the engine rpm range. The PN 1801 comes equipped with an electric choke for easy cold start and performance.

Good luck with your project, your friend is one lucky dude!

Source: edelbrock.com

To Swap or not to swap, That is the Question?

I have an ’88 Monte Carlo SS with a 358 with a 700-R4. I just put it together, but now I want to go fuel-injected. What are the big differences between building an LS motor or buying an EFI carb replacement bolt-on kit? I read about the Holley Avenger EFI kit, and it seems like a good, easy-to-install product. However, given the price, I was thinking I could buy an LS1 with the transmission. Yes, it might be more work, but I am a mechanic in the Air Force and work on many different vehicles, so I’m up for the challenge. I’m ready to take the T-tops off and scream down the road again!

A1C BishopLangley AFBHampton, VA

We’re sure you work on your fair share of unique vehicles: officers’ cars, fueling rigs, equipment movers, and airframe tugs. This gives you a wide experience base for working on just about anything. Don’t ask us to talk you out of an LS engine swap for your little G-body. That is one sweet conversion that really upgrades the performance and driveability of your Monte into the 21st century. The price of engine and transmission combos out of wrecking yards has really made the swaps affordable. You can pick up 5.3L engines hooked to a 4L60E for reasonable prices. You can even step up to 6.0L truck engine combos for not too much more money. These engines will run for a couple hundred thousand miles before they need major overhauls. The performance bolt-ons are everywhere, and the swap kits on the market make the install painless. Check with Muscle Rods for a very nice swap kit that comes complete with engine mounts, a trans crossmember, and headers. The LS swap will give your car much better fuel economy than just an EFI swap on your Gen I small-block. You can buy the engine and transmission with the complete engine and transmission harness and integrate this wiring into your Monte. The electrical conversion will be the toughest part of the swap. Again, there are tons of people out there who can help. Check with the folks at Street and Performance for anything else you may need for your swap. From engine mounts to engine accessories to help with calibration and wiring, they have it all.

Adding the Holley Avenger EFI is also a very nice upgrade. With either the swap or the Avenger EFI you’ll need to upgrade your fuel system to a high-pressure system so that point is moot. It’s basically up to you. How much time do you want your Monte down, since you want to be screaming down the road with the T-tops off? The engine swap can turn into a longer project, depending on your goals. If you pick up an installable engine and transmission combo, you could knock out the swap in a month or two. The fuel-injection system swap could be a weekend if you play your cards right. Again, we’re not going to try to talk you out of the swap. Both are very viable upgrades to your car. Hope we’ve helped you in your decision.

Sources: brphotrods.com, holley.com, hotrodlane.cc

EGR Feed

I purchased a ZZ4 crate engine from GM, and on the manifold, in the plenum under the carburetor, there are two portholes. Are these holes supposed to be plugged up, or do I leave them alone? They are under the carburetor, and I wasn’t sure if they would let any fuel get out of the manifold. Thanks!

ChrisStaten Island, NY

The holes you see in the floor of the manifold plenum are the ports that introduce exhaust gases into the intake manifold when using an EGR valve. When the ZZ4 engine package was in development, it was originally designed as an emissions-legal engine swap package for third-generation Camaros and Firebirds by GM Performance Parts. This engine was a direct replacement for the LG4 and L69 carbureted 305-cid engines that were originally installed in these Camaros. Developing this package, we didn’t know if we were going to need an EGR valve to meet California emissions standards. The ZZ4 engine is equipped with L98 Corvette aluminum heads, which do not have an exhaust crossover to feed the EGR plumbing in that manifold. It was our intention that if we needed exhaust for the EGR, we would feed it externally from a fitting in the passenger-side exhaust manifold. Luckily, we were able to design the camshaft in a way to reduce NOX emissions and not need the EGR system.

During the development we ran both a standard inlet manifold (with no EGR provisions) and the manifold on your engine. On the dyno, the EGR-style manifold actually made slightly more horsepower. The ports on the floor of the plenum are deadheaded at the block-off plate beside the carburetor. Any fuel that builds up in the ports is drawn back into the airstream without any consequence.

The ZZ3 engine was always intended to be a dual-purpose engine. It had to produce at least 300 hp in Emission trim, and make as much horsepower as the previous ZZ2 GM crate engine. Luckily, we were able to meet both bogies and the rest is history. The ZZZ-ZZ4 engine is the best-selling OE crate engine of all time.CHP

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